Resources

Other Useful Stuff

Assignment 2: Box Office Trivia

Introduction

The goal of this assignment is to produce OCaml code that will help you answer
a set of questions about the top-grossing films in movie history.
To get started, download the tarball located here.
Unzip and untar the code and data by typing the following commands at a unix prompt.

$ tar xfz a2.tgz

You should find that the tarball contains the following items.

.merlin: This file contains directives for Merlin to find your source code and additional files after you have compiled.

part1.ml: This file contains list-processing problems for you to complete as part 1 of the assignment.

query.ml: This file is mostly blank. You will write a set of functions
to analyze lists of movies as part 2 of the assignment.

main.ml: This file contains the driver for the program. Don't modify this file, but
you can take a look to see how it's organized. It uses the module Arg to parse command line
arguments in a nice way.

io.ml: This utility file contains a set of useful routines for
parsing and printing movie files. Don't modify it, but feel free to take a look to
see how it's organized. If you'd like to parse and print other
simple text files using OCaml, this code could be a starting point.

README.txt: Report your answers to the movie trivia questions in this file.
Also, explain any unusual design decisions or problems you had here. Suggestions for improving
this assignment are also welcome.

Makefile: Type make all to compile your code and
create an executable you can run to help you answer the key boxoffice trivia questions.

data: This directory contains the data you need to answer the
questions asked on this assignment.
The data was downloaded and processed in May 2012, so it will not be up to date --
films like the The Hunger Games will have continued to rack up the dollars over the
last few years, and new movies will have been released. That's okay. In order to make it easy
to verify your answers, you are required to use the data we provide as opposed to more recent data
that you download from other sites.
There is one file for each movie rating category (G, PG, PG-13, R) and one file for all-time
inflation-adjusted gross movies. There are also a couple of small files you can use for
testing. You will find that the data in the files comes in an arbitrary order.

Part 1: Lists

Examine the contents of the file part1.ml and answer the questions found therein.
This file must typecheck and compile when you hand it in.

Part 2: Box Office Analysis in OCaml

The file query.ml is missing a bunch of functions that you need to code.
See the file for details. Your goal should be to focus first on this file independently
of any of the other files.
You will use these functions to query just a few data files. However, we will test
your functions thoroughly when grading them (and you should test them thoroughly when
writing them). They should operate correctly on all possible inputs. At the bottom
of the file there is some sample infrastructure for unit tests that you may use as a model for
your own testing.

Since the data files you are working with are relatively small, you should not overly concern
yourself with the efficiency of your code -- though needlessly or egregiously inefficient solutions
should be avoided. Your main goals are correctness, clarity and good style. Be sure to refer
to our style guide.

We suggest you implement the functions in part 2 in the following order.

Part 3: Answering the Box Office Trivia Questions

Scripting is a kind of functional programming: Scripts take data files (often representing lists)
as inputs and produce new data files as outputs.
Like functions in a functional program, scripts often compose: you can pipe the output on stdout of
one script into the input on stdin of another script.

When you have finished coding and thoroughly testing the functions in query.ml,
compile the entire application by typing "make" at a shell prompt in your code directory.
To find out what you can do with your script, type the following at a shell prompt.

./boxoffice -help

You should see a list of options you can use. As a simple sanity check to make sure
things are working properly, type the following:

./boxoffice -echo < data/trial1.txt

The above command should send the contents of the trial1.txt data file out on to standard output.
We also included that test as a part of your Makefile so you can also type the following to check
your setup.

make check

Another command you might try is this one:

./boxoffice -take 1 < data/G.txt

What does it do? Recall that the pipe operator (vertical bar) allows you to send the output of
one command in to the input of another command. With that in mind, what does the following do?

./boxoffice -sort-gross < data/G.txt | ./boxoffice -take 1

Now, take a look inside the makefile. You will see the clause for compiling
boxoffice at the top. At the bottom, you'll see the clause for "topG". If you
type:

make topG

you'll see the same thing. Feel free to add your own commands to the file.

To Do: Use your script to answer the questions about boxoffice trivia
posed in the README.txt file. In addition to reporting the answers to the questions,
report the scripting commands you used to find the answers. Try to make the script do
as much work as you can. If possible, use a series of calls to your script to produce
only the data you need to answer the question and no more. (This may not be possible.)

Handin Instructions

This problem set is to be done individually.

You must hand in these files to dropbox:

part1.ml -- this file contains the list processing problems

query.ml -- this file contains the movie processing functions

README.txt -- this file contains written answers

Please make sure you submit your solutions, not the blank stubs you downloaded.

Important notes about grading:

Rec: For this assignment, you may add the rec keyword to any of the let statements that
define functions if you would like the function to call itself. And in the other direction, a function for which we have given
you a let rec needn't call itself, for example, if you have defined a recursive auxiliary function to use instead.

Modules:For this assignment, you should not use functions from the List module,
nor the built-in @ operator. You should code these functions "from first principles"
using recursion. Do not use functions from any module as a reference to help you
re-implement these functions.

Compile errors: All programs that you submit must type check and compile.
Programs that do not compile will be subject to a penalty in addition to
the deduction for the bug that causes the failure to compile. If you are
having trouble getting your
assignment to compile, please visit office hours. If you run out of
time, it is better to comment out the parts that do not compile and
hand in a file that compiles, rather than handing in a more complete
file that does not compile.

Missing functions: We will be using an automatic grading
script, so it is crucial that you name
your functions and order their arguments according to the problem set
instructions, and that you place the functions in the correct files. Otherwise
you may not receive credit for a working but misnamed function.

Code style: Finally, please pay attention to style. Refer
to the OCaml style guide and lecture notes.
Ugly code is not fun to debug, nor to grade. Take the extra time to think through
the problems and find the most elegant solutions before coding them up.
Good programming style is also required on all the subsequent assignments.